The present invention relates to a navigation system for providing a driver of a vehicle with information on a route to a destination when the vehicle is driven along a route unfamiliar to the driver.
A vehicular navigation system is a system which searches for an optimal route from the present position of the vehicle or from a specified starting point to a destination based on inputted data such as the destination data, and provides the driver with information on a route to reach the destination, when the vehicle is driven along a road unfamiliar to the driver, by displaying a road map on a screen of a display unit, based on the suggested optimal route, and by displaying the suggested route or the present position of the vehicle on the map.
With regard to the display on the screen, a system has been known in the past in which a route is searched from the present position of the vehicle or from a destination based on inputted data such as a destination, a transit point, etc., and a suggested route is displayed on a map or the advancing direction is displayed by an arrow on an enlarged map. FIG. 28 represents a map, which shows a route to guide the vehicle to a destination (park marked with an asterisk) via a highway shown by a white line (outlined line). FIG. 29 is an enlarged view of an area near a branch point for guiding toward a route from PARI to an airport, and an arrow indicating the advancing direction from the branch point and a message "5.0 miles; 10 minutes to the destination" is displayed.
In a conventional type system as described above, the suggested route is drawn on a map as shown in FIG. 28, and the driver must find out the turning point and the turning direction by watching the map. Thus, it takes some time until the driver fully understands the situation. Also, in case the present position of the vehicle, the advancing direction, or the route already driven are displayed by the same magnification factor, it is difficult for the driver to discriminate between the information necessary for immediate guiding and other information. Because a large amount of information is displayed in addition to the information on the present position and it is not always easy to recognize the information on the present position, the display is not always satisfactory in terms of recognizability. For example, in case a road is curved, it is sometimes difficult to judge whether or not the road is curved.
Also, when an area is enlarged in the map as shown in FIG. 29 and the next guide branch point is not in the displayed area, this is inconvenient because the driver cannot find out the direction to be taken from that guide branch point. To solve this problem, it has been proposed to indicate two advancing directions for adjacent intersections on the suggested route. However, by simply displaying two advancing directions, it is not easy to judge which of the advancing directions should be chosen, and it is difficult to find out the next advancing direction.